Fatigue in materials is the result of cumulative damage processes that are usually induced by repeated loading cycles. Energy dissipation associated with irreversible damage, accompanied by the evolution of heat. The relation between stress and strain exhibits a lag between input and output termed hysteresis. Due to this lag, the forward path is different than the backward forming a loop. Evolution of stress-strain hysteresis in alumina is observed. Hysteresis as a structural feature has been recorded in magnesia, zirconia, SiC/SiC and Si 3 N 4 . The mean stress has been defined and its effect in alumina and yttria stabilized tetragonal zirconia inducing microcracks and damage is discussed in this chapter. Further, the mean stress effect is observed also in Si 3 N 4 and the fatigue failure is expressed in terms of the relation between stress amplitude and the mean stress.